I am runing Windows 8.1 on a Toshiba Satellite L875.  Intel(R) Core(TM)  CPU @ 2.40 GHz  2.40 GHz  RAM 4GB

 

When I tap on the "enter" button to make the lock screen go away so I can enter my password it bounces up and then down.   I have also been unable to choose anything from menus.  When I pull the menu down it bounces back up before I can make a selection. Another thing that is happening is that when I downloaded a file I couldn't save it to either my desktop or a new folder. I can save changes to existing files though. This all started at the same time.  I opened my computer on Monday and it's been this way ever since.  I'm hoping someone knows what this is and if it's not to far above my capabilities that I might repair it myself.  Thanks.